Co2 refrigeration system for ice-playing surface

ABSTRACT

A CO 2  refrigeration system comprises a CO 2  circuit. In a compression stage of the circuit, CO 2  refrigerant is compressed to a supracompression state. In a cooling stage, the CO 2  refrigerant from the compression stage releases heat. A pressure-regulating unit in a line extending from the cooling stage to one side of a heat exchanger maintains a pressure differential. A second refrigerant cycles in a cooling circuit between a second side of the heat exchanger and an ice-playing surface. The second refrigerant absorbs heat from the ice-playing surface and releases heat to the CO 2  refrigerant in the heat exchanger.

CROSS-REFERENCE TO RELATED APPLICATION

The present application claims priority on Canadian Patent Application No. 2,771,113 filed on Mar. 8, 2012, incorporated herewith by reference.

FIELD OF THE APPLICATION

The present application relates to refrigeration systems used for cooling ice-playing surfaces such as hockey rinks, skating rinks, curling sheets, etc. and, more particularly, to such refrigeration systems using CO₂ as refrigerant.

BACKGROUND OF THE ART

With the growing concern for global warming, the use of chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs) as refrigerant has been identified as having a negative impact on the environment. These chemicals have non-negligible ozone-depletion potential and/or global-warming potential.

As alternatives to CFCs and HCFCs, ammonia, hydrocarbons and CO₂ are used as refrigerants. Although ammonia and hydrocarbons have negligible ozone-depletion potential and global-warming potential as does CO₂, these refrigerants are highly flammable and therefore represent a risk to local safety. On the other hand, CO₂ is environmentally benign and locally safe.

However, CO₂ refrigerant must be compressed to high pressures (e.g., supra-compressed or transcritically compressed) to optimize the efficiency of CO₂ refrigeration systems. Accordingly, existing CO₂ refrigeration systems require numerous components, and this may have an impact on the cost efficiency of such systems. It is therefore desirable to simplify CO₂ refrigeration systems.

SUMMARY OF THE APPLICATION

It is therefore an aim of the present disclosure to provide a CO₂ refrigeration system for ice-playing surfaces that addresses issues associated with the prior art.

Therefore, in accordance with the present application, there is provided a CO₂ refrigeration system comprising: a CO₂ circuit comprising a compression stage in which CO₂ refrigerant is compressed to at least a supracompression state, a cooling stage in which the CO₂ refrigerant from the compression stage releases heat, a pressure-regulating unit in a line extending from the cooling stage to one side of a heat exchanger to maintain a pressure differential therebetween; and a cooling circuit in which cycles a second refrigerant between a second side of the heat exchanger and an ice-playing surface, such that the second refrigerant absorbs heat from the ice-playing surface and releases heat to the CO₂ refrigerant in the heat exchanger.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a block diagram of a CO₂ refrigeration system for an ice-playing surface in accordance with an embodiment of the present disclosure; and

FIG. 2 is a block diagram of the CO₂ refrigeration system of FIG. 1 with additional components.

DESCRIPTION OF PREFERRED EMBODIMENTS

Referring to the drawings and more particularly to FIG. 1, there is illustrated a CO₂ refrigeration system in accordance with an embodiment of the present disclosure. The CO₂ refrigeration system is of the type used to cool ice-playing surfaces, such as the skating rinks, curling sheets, etc. The CO₂ refrigeration system of FIG. 1 comprises two different circuits in a heat exchange relation.

One of the circuits is CO₂ circuit 10. The CO₂ circuit 10 comprises a supra-compression stage 12. The supra-compression stage 12 comprises one or more compressors that compress CO₂ refrigerant in a gaseous state to a supra-compressed state. In an embodiment, the CO₂ refrigerant is compressed to a transcritical state.

While in the supra-compressed or transcritical state, the CO₂ refrigerant is fed to a gas cooling stage 14. In the gas cooling stage 14, the CO₂ refrigerant in the supra-compressed or transcritical state releases heat. The heat release may be in some form of heat reclaiming. For instance, heat is reclaimed from the CO₂ refrigerant by heating up water (e.g., water tank), or by heating equipment (e.g., ice melting equipment, hot air blowers, etc.). The gas cooling stage 14 may consists of one or more heat exchangers for the CO₂ refrigerant to be in the heat exchange relation with a secondary refrigerant (e.g., glycol) to recuperate the heat and direct it to remotely located heating equipment. The gas cooling stage 14 may comprises numerous heat exchange components to remove heat from the CO₂ refrigerant. For instance, the coiling stage 14 may comprises a plurality of heating units, with valves provided in relation to the plurality of heating unit to individually control an amount of CO₂ refrigerant directed to each of the heating units. The fan of each heating unit may be controlled by a controller as a function of a temperature demand and of the amount of CO₂ refrigerant fed to each heating unit.

A pressure regulating unit 16 is positioned in the circuit 10 downstream of the gas cooling stage 14, and upstream of a heat exchanger(s) 18. The pressure regulating unit 16 may be any valve or arrangement of valves, etc. that will maintain a high pressure of CO₂ in the circuit 10 upstream thereof. Therefore, the CO₂ refrigerant is kept in the supra-compressed or transcritical state between the supra compression stage 12 and the pressure regulating unit 16, to optimize the efficiency of the gas cooling stage 14. Because of the pressure regulating unit 16, the CO₂ refrigerant is fed at a lowered pressure to the side of the heat exchanger 18 in the CO₂ circuit 10. The CO₂ refrigerant is then directed to the supra compression stage 12, to complete a refrigeration cycle in the circuit 10.

The CO₂ refrigerant in the circuit 10 is in a heat exchange relation with another refrigerant in a cooling circuit 20, by way of the heat exchanger 18. The cooling circuit 20 extends from the second side of the heat exchanger 18 to coils or pipes located under an ice-playing surface, or to a heat exchanger that will ultimately absorb heat from the ice-playing surface. The refrigerant circulating in the cooling circuit 20 may be brine, water, glycol or any appropriate refrigerant that is circulated in the coils of pipes of an ice-playing surface. In the heat exchanger 18, the CO₂ refrigerant and the ice-playing surface refrigerant are solely in a heat exchange relation and, hence, do not mix. In an embodiment, the heat exchanger 18 is a shell-and-tube type of heat exchanger. Therefore, the shell of the heat exchanger 18 may act as a reservoir for CO₂ refrigerant of the CO₂ circuit 10, with the line relating to heat exchanger 18 to the supra compression stage 12 being connected to a top of the reservoir of the heat exchanger 18 for the suction of gaseous CO₂ refrigerant. The tubes would define the second side of the heat exchanger 18 and thus the second refrigerant would circulate therein. Alternatively, the network of pipes relating the heat exchanger 18 to the supra compression stage 12 may act as reservoir. Additional components may be provided to ensure that the CO₂ refrigerant reaching the compressors of the supra-compression stage 12 is in a gaseous state.

It is observed that the CO₂ refrigeration system for the ice-playing surface of FIG. 1 distinguishes by its simplicity and minimum amount of components.

Referring to FIG. 2, an alternative embodiment of this CO₂ refrigeration system is shown with additional components. The CO₂ refrigeration circuit 10 features a condensation reservoir 30 that is positioned between the heat exchanger 18 and the supra-compression stage 12. The condensation reservoir 30 collects CO₂ in a generally liquid state. In an embodiment, the line connecting the condensation reservoir 30 to the supra compression stage 12 are positioned atop the condensation reservoir 30 to collect CO₂ that is in a generally gaseous state.

This cooling circuit 20 may feature a pump 32 that will circulate the ice-playing surface refrigerant between the heat exchanger 18 and the coils or pipes of the ice-playing surface 34. The pump 32 may be positioned either upstream or downstream of the heat exchanger 18.

It is within the ambit of the present invention to cover any obvious modifications of the embodiments described herein, provided such modifications fall within the scope of the appended claims. 

1. A CO₂ refrigeration system comprising: a CO₂ circuit comprising a compression stage in which CO₂ refrigerant is compressed to at least a supracompression state, a cooling stage in which the CO₂ refrigerant from the compression stage releases heat, a pressure-regulating unit in a line extending from the cooling stage to one side of a heat exchanger to maintain a pressure differential therebetween; and a cooling circuit in which cycles a second refrigerant between a second side of the heat exchanger and an ice-playing surface, such that the second refrigerant absorbs heat from the ice-playing surface and releases heat to the CO₂ refrigerant in the heat exchanger.
 2. The CO₂ refrigeration system according to claim 1, wherein the cooling stage comprises at least one of a gas-cooling unit, a heat-reclaim exchanger, and a heating unit.
 3. The CO₂ refrigeration system according to claim 2, comprising a plurality of the heating unit, with valves provided in relation to the plurality of heating unit to individually control an amount of CO₂ refrigerant directed to each said heating unit.
 4. The CO₂ refrigeration system according to claim 3, wherein a fan of each said heating unit is controlled by a controller as a function of a temperature demand and of said amount of CO₂ refrigerant.
 5. The CO₂ refrigeration system according to claim 1, further comprising at least one pump in the cooling circuit to induce a flow of the CO₂ refrigerant therein.
 6. The CO₂ refrigeration system according to claim 1, further comprising a CO₂ condensation reservoir between the heat exchanger and the compression stage.
 7. The CO₂ refrigeration system according to claim 1, further comprising a line extending directly from the heat exchanger to the compression stage.
 8. The CO₂ refrigeration system according to claim 1, wherein the heat exchanger is a shell and tube type of heat exchanger, with the CO₂ circuit side of the heat exchanger being the shell, the cooling side of the heat exchanger being the tubes.
 9. The CO₂ refrigeration system according to claim 1, wherein the cooling circuit comprises pipes under the ice-playing surface in which circulates the CO₂ refrigerant to refrigerate the ice-playing surface.
 10. The CO₂ refrigeration system according to claim 1, wherein the CO₂ refrigerant in the CO₂ circuit is compressed to a transcritical state.
 11. A CO₂ refrigeration system comprising: a CO₂ circuit comprising a compression stage in which CO₂ refrigerant is compressed to at least a supracompression state, a cooling stage in which the CO₂ refrigerant from the compression stage releases heat, a pressure-regulating unit in a line extending from the cooling stage to one side of a heat exchanger to maintain a pressure differential therebetween; and a cooling circuit without a reservoir in which cycles a second refrigerant between a second side of the heat exchanger and an ice-playing surface, such that the second refrigerant absorbs heat from the ice-playing surface and releases heat to the CO₂ refrigerant in the heat exchanger.
 12. The CO₂ refrigeration system according to claim 11, wherein the cooling stage comprises at least one of a gas-cooling unit, a heat-reclaim exchanger, and a heating unit.
 13. The CO₂ refrigeration system according to claim 12, comprising a plurality of the heating unit, with valves provided in relation to the plurality of heating unit to individually control an amount of CO₂ refrigerant directed to each said heating unit.
 14. The CO₂ refrigeration system according to claim 13, wherein a fan of each said heating unit is controlled by a controller as a function of a temperature demand and of said amount of CO₂ refrigerant.
 15. The CO₂ refrigeration system according to claim 11, further comprising at least one pump in the cooling circuit to induce a flow of the second refrigerant therein.
 16. The CO₂ refrigeration system according to claim 11, further comprising a CO₂ condensation reservoir between the heat exchanger and the compression stage.
 17. The CO₂ refrigeration system according to claim 11, further comprising a line extending directly from the heat exchanger to the compression stage.
 18. The CO₂ refrigeration system according to claim 11, wherein the heat exchanger is a shell and tube type of heat exchanger, with the CO₂ circuit side of the heat exchanger being the shell, the cooling side of the heat exchanger being the tubes.
 19. The CO₂ refrigeration system according to claim 11, wherein the cooling circuit comprises pipes under the ice-playing surface in which circulates the CO₂ refrigerant to refrigerate the ice-playing surface.
 20. The CO₂ refrigeration system according to claim 11, wherein the CO₂ refrigerant in the CO₂ circuit is compressed to a transcritical state. 